Electrical contact device having resiliently mounted contact



g- 1950 J. KUPERUS ELECTRICAL CONTACT DEVICE HAVING RESILIENTLY MOUNTED CONTACT 2 Sheets-Sheet 1 Filed April 22. 1946 .ZYZ .Jd. E .112

nun/ML 59500516) I l JAFKUPERUZS' INVEN TOR.

MM*M ATTORNEY! Aug. 8, 1950 J. KUPERUS 2,518,030

ELECTRICAL CONTACT DEVICE HAVING RESILIENTLY MOUNTED CONTACT Filed April 22. 1946 2 Sheets-Sheet 2 nan/mu. FREQ/576% @17 1 "-15 14 16 l GA 4 jig 622.

wanna/e QMNKZZPEQZZS INVENTOR.

yh/M ATTUMYP Patented Aug. 8, 1950 ELECTRICAL CONTACT DEVICE HAVING RESILIENTLY MOUNTED CONTACT Jan Kuperus, Eindhoven, Netherlands, assignor,

by mesne assignments, to Hartford National Bank and Trust Company, Hartford, Conn, as

trustee Application April 22, 1946, Serial No. 663,936 In the Netherlands January 21, 1942 Section 1, Public Law 690, August 8, 1946 Patent expires January 21, 1962 6 Claims.

This invention relates to a contact. device for closing and interrupting an electric current wherein a driving arm is set into motion by an actuating means such as an electromagnet, said arm being mechanically coupled to an auxiliary spring carrying one of two co-operating contacts.

Conventional devices generally comprise a socalled stationary contact and a movable contact co-operating with the latter, as well as driving means for the movable contact. It may occur that the stationary contact is more or less movable. In these cases also it will be referred to as stationary contact. If upon actuation the position of the movable contact of the contact device is caused to change with normal speed from the completely opened into the completely closed state with reference to the stationary contact, the movable contact and its driving means traverse a certain path. The position occupied by them when the two co-operating contacts engage each other for the first time is called the "contact position and the relative speed of the contacts at this moment the closing speed.

In an operative contact device the co-operating contacts will generally have a relative speed at the moment that the contact position is attained, so that an impact occurs between the contacts which are in part resilient. Consequently, the relative speed of the co-operating contacts has decreased after the impact and changed in sign. The contacts move from each other until the kinetic energy has been transformed into potential energy. Under the action of the driving mechanism or resilient forces the contacts approach each other again until a second impact takes place further decreasing the relative speed. This action is repeated until the relative speed between contacts has diminished to a point where they remain definitely closed. Before the contacts are closed definitely, the current is thus closed and interrupted a large number of times within a small period of time.

This effect, which is usually referred to as hammering, must in general be considered as detrimental. Thus, among the devices to which the invention applies are the so-called vibrators," that is to say contact devices for transforming direct current into alternating current or inversely. In this case the hammering involves the formation of sparks, due to which the chanically coupled to a driving arm, the spring having an individual vibratory motion. The driving arm is set into periodic motion by an actuating means, such as an'electromagnet, so that the contact carried by the spring, as a result of the individual vibratory motion of the spring and the periodic movement of the arm, describes a composite movement.

According to the invention, the natural frequency of the auxiliary spring is adapted to the movement of the driving arm in such manner that at the moment when the latter attains the contact position the relative speed of the contacts is at the optimum degree required for a prescribed condition of operation.

If, now, in particular the hammering effect should be avoided, the optimum chosen will be the zero value so that at the moment when the driving arm attains the contact position the relative speed of the contacts is small or substantially zero. If, on the other hand, it is desired to have a rapidly operating switch action, the optimum degree chosen is the highest relative speed chtainable.

In order that the invention may be more clearly understood and readily carried into effect, it will now be explained more fully by reference to the accompanying drawings.

Fig. 1a is a plan view of a preferred embodiment of a vibrator structure in accordance with the invention, while Fig. 1b is a graph illustrative of the operation of the vibrator.

Fig. 2 is a plan view of a modification of the vibrator structure shown in Fig. 1a.

Fig. 3a is a plan view of another preferred embodiment of a vibrator structure, while Fig. 3b is a graph illustrative of the operation thereof.

' Fig. 4 is a plan view of still another preferred embodiment of a vibrator structure in accordance with the invention.

Fig. 5a is a plan view of a preferred embodiment of a relay in accordance with the invention, and Fig- 5b is a graph illustrative of its operaion.

Fig. 6a is a plan view of a further embodiment of a relay, and Fig. 6b is a graph illustrating the relay operation.

Fig. 7a is a plan view of yet another embodiment of a vibrator structure, and Fig. 7b is a graph illustrative of the vibrator action.

In the construction shown in Fig. 1a the driving arm I which is set into periodic motion by an actuating mechanism such as an electromagnet has provided on it an auxiliary spring 2. The latter carries the movable contact 3 which cooperates with the stationary contact I. Fig. 11) represents in a path-time diagram the movement of the parts of the contact device shown in Fig. la. The time t is plotted on the horizontal tacts engage each other.

axis and the path S on the vertical axis. In such a diagram the speed is proportional tothe oscillation of the considered curve. The path of the driving'arm is indicated by a, b being the path which would be traversed by the movable contact if the mechanical connection with the driving arm were rigid and the stationary contact 4 were not present. Due to the resilient connection 2 and the stationary contact 4, which serves as the abutment, the movable contact will make a composite movement. The latter is indicated diagrammatically by c and is to be considered as the superposition of the natural oscillation of the auxiliary spring 2 and the contact 3 on the movement of the driving arm i.

For simplicity's sake it is assumed in the figures that the driving arm moves in parallel to itself. In reality the driving arm, which may be moved, for example, by means of an electro-magnet, will usually have the form of a spring or a rotary arm, so that upon actuation, an angular rotation of the arm occurs. It has been found, however, that this does not make any difference. In the part of path which is indicated by AB contact 3 engages with contact 8. In point B the driving arm i starts to withdraw the contact 3. The initial speed of the contact 3 is zero.

With the aid of mechanics the path c of the contact 3 and hence the closing speed (which is equal to the slope of the path 0 in point D) may be calculated from the known movement of the driving arm i and the initial speed of the contact 3. This appears to be a function of the ratio which exists between the frequencies of movement of the driving arm and the natural frequency of the auxiliary spring 2 and the contact 3 secured thereto. For reducing the closing speed to approach zero it appears to be necessary to choose the said ratio of such value that the auxiliary spring 2 with the contact 3 during the time that the contacts 3 and 4 are open (in Fig. 1 from B to D) describes an odd number of half waves. Since this odd number may be chosen at will, a series of ratios is found. The desired ratio of frequency is realised in practice by means of a suitable choice of the size and the rigidity of the auxiliary spring and, if the case may be, of the driving arm, which has the form of a spring, and of the mass of the contact 3. In the construction shown in Fig. 2, a subsequent very fine adjustment of this ratio may still be obtained by varying the diameter of the distance ring 5 which is provided between the main spring G and the auxiliary spring I. An increase of this diameter results in a shortening of the auxiliary spring 1, i. e. in an increase of the natural frequency thereof. It is thus possible to reduce the closing speed to zero or substantially to zero. This may be controlled with the aid of a strobescope. The presence or the absence of the hammering effect may be ascertained with the aid of a cathode-ray oscillograph in a connection suitable for this purpose.

Fig. 3a shows another embodiment of the invention. The wea auxiliary spring 8, which carries the stationary contact 9, is only coupled to the driving arm H], which carries the movable contact ll, during the period in which the con- Figure 3b shows the path-time diagram for the moving elements in the device of Fig. 3a. The curve d represents the path of the moving contact II and curve e the path of the stationary contact 9. It will be seen that the frequency of contact 9 is twice that of contact II and that contacts 9 and ll engage each other from E to F. The en; spring 8 is so weak that it substantially does not disturb the movement of the driving arm. The contacts 9 and l I are separated in point F. Their relative speed in thispoint approaches zero inasmuch as the relative speed of contacts 9 and II depends on the slopes of curves e and (2, respectively, which slopes are substantially coincident at point F. This can be seen from the coincidence of the tangents with the curves (2 and e in point F. During the time that the contacts 9 and H are open (in Fig. 3b from F to G) the stationary contact carries out a natural oscillation which is adapted to the movement of the driving arm it by means of a suitable choice of the size and the rigidity of the auxiliary spring 8 and of the magnitude of the mass of the contact Q in such manner that the closing speed in point G is zero. There is again a series of frequencies for which this is the case. It is also possible to secure the auxiliary spring in an electrically insulated manner and provided with a separate supply conductor 52 to the driving arm ill without involving any essential change in the movement of the contacts. This is represented in Fig. 4.

In Fig. 5a, 13 is the driving arm of a contact device which does not operate periodically. It has fastened on it an auxiliary spring I 3 carry ing the movable contact l5 which co-operat-es with the stationary contact It. In the position of rest, the auxiliary spring H3 bears with a certain preliminary tension against the abutment N. Fig. 5b represents the path-time diagram, in which i is the path of the driving arm, 9 is the path which would be traversed by the movable contact if the abutment i'i and the contact it were absent and the auxiliary spring it were rigid and h is the path traversed by the movable contact. With each form of movement of the driving arm there exists a series of values of the period of oscillation of the system constituted by the auxiliary spring M and the mass of the contact I5, for which the closing speed (the slope of "curve It in point H) is zero.

In Fig. 6a the stationary contact i8 is resiliently arranged on an auxiliary spring it with which an abutment zll'is connected in an insulated manner. In'the position of rest shown, the auxiliary spring I 9 has a preliminary tension. If the driving arm ill in the figure moves downwardlythe spring I 9, jointly with the masses fastened thereto; will carry out a natural oscillation, due to which the contact l8 will traverse a path i which is to be'considered as an oscillation about the position of equilibrium The path of the driving arm is represented by k. Here again there is a series of values for the priod of oscillation, for which th closing speed becomes zero. This can be seen from the figure by the coincidence of the tangents with the curves 1' and k and the point I. I

It can be seen from Figs. 1b and 5b that the paths 0 and a have also points where the speed of the movable contact is greater than that of the driving arm.

In Fig. 1b this is the case, for example, in point C where the inclination of curve 0 is larger than that of the curves b and a. This may be utilised, for example, in contact devices in which a contact should close a current (periodically or not periodically) only during a very short time. In this case a high relative closing speed of the contacts is advantageous, since in this case the contacts will be rapidly separated due to the great resilient forces produced. Fig. 7a is an embodiment thereof, applied to a periodically operating contact device. The abutment 25 is engaged by the auxiliary spring 23 with a preliminary tension. Fig. 71) represents the associated path-time diagram. In this diagram, i is the path of the movable contact 24 and m the path which would be traversed by the latter if the spring 23 were rigid and the abutment 25 were not present. The driving arm 22 moves downwardly and immediately thereafter moves upwardly under the action of known driving means. The period of oscillation of the oscillatory system constituted by the auxiliary spring 23 and the mass of the contact 24 is adapted to the movement of the driv-- ing arm 22 in such manner that the closing speed is considerably greater than the maximum speed of the driving arm, as it appears from the slopes of the curves land m in the points J and K.

Contact devices according to the invention exhibit the characteristic of a long life and a simple construction. As compared with the adjustment required for the afore-mentioned known solution, the adjustment in mass production, even for compact devices, has been rendered much simpler, resulting in a considerable decrease in cost price.

I claim:

1. An electrical contact device comprising two cooperating contact members, a driving arm, actuating means to set said driving arm into motion, and an auxiliary spring arranged to be actuated by said driving arm, said spring carrying one of said cooperating contacts and having an individual vibratory motion which is a harmonic of the frequency of movement of said am, the movement of said arm causing said one contact to move in and out of engagement with the other contact, said spring having a natural vibratory frequency whose rate relative to the frequency of movement of said arm is such whereby at the moment said arm attains the closed contact position, the relative speed of said cooperating contacts as a result of the composite movement of said one contact is at the optimum degree for a prescribed condition of operation.

2. An electrical contact device comprising two cooperating contact members, a driving arm, actuating means to set said driving arm into motion, and an auxiliary spring mechanically coupled to said driving arm, said spring carrying one of said cooperating contacts and having an individual vibratory motion which is a harmonic of the frequency of movement of said arm, the movement of said arm causing said one contact to move in and out of engagement with the other contact, said spring having a natural vibratory frequency whose rate relative to the frequency of movement of said arm is such whereby at the moment said arm attains the closed contact position, the relative speed of said cooperating contacts as a result of the composite movement of said one contact approaches zero.

3. An electrical contact device comprising two cooperating contact members, a driving arm, actuating means to set said driving arm into motion, and an auxiliary spring mechanically coupled to said driving arm, said spring carrying one of said cooperating contacts and having an individul vibratory motion, the movement of said arm causing said one contact to move in and out oi engagement with the other contact, the ratio of the natural vibratory frequency of said spring to the frequency of movement of said arm being such that said one contact oscillates an odd numher of half waves during the period that said cooperating contacts are open.

4. An electrical contact device comprising two cooperating contact members, a driving arm, actuating means to set said driving arm into periodic motion, and an auxiliary spring mechanically coupled to said driving arm, said spring carrying one of said contacts and having an individual vibratory motion which is a harmonic of the frequency of movement of said arm, the movement of said arm causing said one contact to move in and out of engagement with the other contact, said spring having a natural vibratory frequency whose rate relative to the frequency of movement of said arm is such whereby at the moment said arm attains the closed contact position, the speed of said one contact, as a result its composite movement is considerably greater than the speed of said driving arm.

5. An electrical contact device comprising two cooperating contact members, a driving arm, electromagnetic actuating means to set said driving arm into periodic motion, an auxiliary flat spring, means to mechanically couple said auxiliary spring to said driving arm in parallel relation therewith, said coupling means including a spacing ring interposed between said driving arm and said auxiliary spring, said spring carrying one of said cooperating contacts and having an individual vibratory motion which is a harmonic of the frequency of movement of said arm, the movement of said arm causing said one contact to move in and out of engagement with the other contact, said spring having a natural vibratory frequency whose rate relative to the frequency of movement of said arm is such whereby at the moment said arm attains the closed contact position the relative speed of said cooperating contacts as a result of the composite movement of said one contact is at the optimum degree for a prescribed condition of operation.

6. An electric contact device comprising two cooperating contact members, a driving arm, actuating means to set said driving arm into motion, an auxiliary spring mechanically coupled to said driving arm, said spring carrying one of said contacts and having an individual vibratory motion which is a harmonic of the frequency of movement of said arm, the movement of said arm causing said one contact to move in and out of engagement with the other contact, and an abutment so positioned against said auxiliary spring as to cause said spring when at rest to bear against said abutment with a predetermined tension, said spring having a natural vibratory frequency whose rate relative to the frequency of movement of said arm is such whereby at the moment the arm attains the contact position the relative speed of said cooperating contacts as a result of the composite movement of said one contact approaches zero.

JAN KUPERUB.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STAI'ES PATENTS 

